1. Field of the Invention
A device for determining the temperature of a glass ceramic plate heated with heat coils or halogen lamps using a temperature sensor which emits a signal for a control circuit corresponding to the temperature of the glass ceramic plate, in which the heat coils or the halogen lamps are positioned in the internal space of a cylindrical vessel-like insulation support, and in which the edge of the insulation body, under spring tension, abuts on the glass ceramic plate heated by the radiation of the heat coils or the halogen lamps.
2. Description of the Prior Art
Such types of devices are in particular used in cooking stoves in which the glass ceramic plate extends over several heating positions predetermined by the position of the insulation support with the heat coils or the halogen lamps. The temperature sensor is also accommodated in the internal space of the insulation support, and heated by the irradiation emitted by the heat coils or the halogen lamps. Since the temperature sensor can follow the temperature changes determined by the switching on and switching off of the heat coils or the halogen lamps more rapidly than the glass ceramic plate, there arise brief control oscillations in the control circuit. If the temperature sensor outside the internal space of the insulation body is brought into heat-conducting connection with the glass ceramic plate, then the brief temperature elevations conditioned by the switching on and switching off the heat coils or the halogen lamps exert little influence on the temperature sensor, since it is only heated by means of the glass ceramic plate. Through the inertia of the glass ceramic plate, that is, its thermal conductivity, a delay arises in the heating of the temperature sensor, which leads to undesirable control characteristics with significant hysteresis. In both cases, sufficient precision cannot be achieved for control of the temperature of the glass ceramic plate.
If the temperature sensor is accommodated in a thermally insulated manner in the internal space of the insulation support, then a portion of the surface of the glass ceramic plate is lost for heating by means of the irradiation.